Solvent fractionation of waxcontaining mixtures



y 1952 E. w. CLARKE 2,604,435

SOLVENT FRACTIONATION OF WAX-CONTAINING MIXTURES Original Filed Sept. 16, 1947 ZL'ADDITIVE EXTM SOLVENT arrzsz INVENTOR.

Hfiorney Patented July 22, 1952 SOLVENT FRACTIONATION F WAX- CONTAINING MIXTURES Edgar WL Clarke; Laurel Springs, N, J., assignor to The AtlanticRefining Company, Philadelphia, Pa.,' a corporation of Pennsylvania 7 Original application September; 16, 1947, Serial 7 No. 774;;230.- Divided and this application November v 1 949, Se'rial No; 125,726

The present invention relates to the treatment of'oily waxed-and more particularly to the sepa ration of wax containing mixtures" into' fractions of higher and lowermelting ipoint; using a solvent comprising acetone andfifan 'ditive'comprising aniline; v f

This application is a division of copending a'p plication, Serial No. 774,230, filed Septeniberfld, 1947, now Patent No. 2,578,510Q'and entitled 'Solvent Fractionation of Wax-ContainingM xtures. The present invention is especiallyapplicable to the deoiling of hydrocarbon waxes containing not more than about 70% of oil, and to-the separation of wax mixtures of low oil content into fractions of different melting point. l'heprocess of the present inventionlmay heapplie'd in the refinin purification,- or-separation of wax stocks such as petroleum slack wax,- crude microcrystalline wax, parafiin waxes, petrolatum wax, b

montan Wax, ceresin, ozokerite, waxes from the destructive or non-destructive hydrogenation of mineral oil, synthetic'hydroca'rbon oil, shale oil, coal, and waxes produced synthetically; by the catalytic reaction of hydrocarbons-or waxes derived from the modified Fischer-Tropsch reaction of carbon "monoxide and hydrogen: 'The process of this invention is'especially applicable in the separation of wax 'mixtures" containing color bodies and oil into a higher melting'wax fraction of light color and low oil content, and

a lower melting wax fraction of darker color and containing most of the oil originallypresent in the wax mixture. I i Y v 1 In accordance Withthis invention, a wax-containing mixture is separated into fractions of higher and lower melting point by countercurrently contacting the wax-containing mixture in an extraction zone with an extraction solvent and a solvent additive or additives at a temperature such that two liquid phases, are formed, one comprising the higher melting wax'fraction with minor amounts of solvent and additive, and the other comprising the lower melting wax fraction with major amounts of solvent and additive, separating the liquid phases from one; another, and removing the solvent and additive from each. Theextraction solvent employed may have a density less than that of the wax, while the additive or additives may have a .densitygreater than that of the wax. However, when the additive or additives are partially immisciblewith the extraction solvent iand are less dense than suchsolvent or the wax, the additive or additives will now countercurrent to the extraction solvent 3Claims. (01.196-17) and will appear with that liquid phase comprising the higher melting wax fraction. 'The success of the process depends upon the control-bf the temperature throughout the extraction zone 'andupon theregulation of the proportions of solvent and additive used, and the points ofintroduction of the wax-containing mixture, the

solvent, and the 'additi've i'nto the extraction Zona.

I The extraction solvent may be defined as'an agent which,'when intimately mixed with a wax-' containing mixture, forms two liquid phases or layers, one comprising a ra-ffinate phase containing mostly wax of higher melting point than the untreated wax and a portion of the 'sclvent',--and the other comprising an extract 'phase tontaining mostly solvent, and 'wax'oflower melting point than the untreated wax, as well as amajor portion of the color bodies and oilori'ginally present in the untreated wax. 1

The solvent additive may; be defined as' an agent used in conjunction with the extraction solvent for the'purpose of modifying the 'char acteristics of the extraction solvent. Theadditive may lower the temperature at which solid wax precipitates out of the extraction solvent, or it may raise the miscibility temperature of the extraction solvent with the wax. However," the additive chosen for a particular-extraction solvent must not excessively lower the selectivity of the extraction solvent at the temperature of. extraction. v The extraction solvent may be employed .in amounts ranging from 1 to 5 volumes of per volume of untreated waxstock, whilejthe additive or additives may be used in amountsranging from 0.05 to 1 volumes, per volume. of untreated wax. q Y Y Q The extraction solvent .whichm'ay be employed in accordance with the present inventionhomprises acetone.

The solvent additive or additives, which are usually employed in amounts constituting not more than 50% by volume of the extraction sol vent, comprise aniline. g r

The process of the present invention-may be carried out in a multi-stage batch countercurrent extraction system or in a continuous countercurrent extraction system, preferably a tower provided with perforated bafiies or containing a packing material such asceramic shapes, tiles, metal wool, or fragments of ceramic material, glass-pumice, carborundum, or concrete.- For most effective operationja temperature gradient is maintained in the system by means of heating or cooling coils or jackets, the temperature increasing in the direction of fiow of the rafiinate or higher melting wax fraction.

The present invention may be further understood with reference to the accompanying drawing which illustrates diagrammatically a continuous extraction system suitable for carrying out the process.

Referring to the drawing, a wax-containing mixture is continuously I introduced, in liquid condition, into the extraction tower I through valve-controlled pipe 2 at a rate of 100 volumes per hour. An extraction solvent comprising acetone is continuously introduced from vessel 3 by means of valve-controlled pipe 4 and manifold 5 into the lower section of the tower above the rafl'inate outlet at a rate of 400 volumes per tower I, the temperature beingcontrolledin the tower by means of coils II through which a heating or cooling medium is circulated as required. The temperature, in the present case, is held constant, for example, at-85" F., the contents being entirely in the liquid phase. The wax stock, being subjected to the action of the solventand additives, iscaused to separate by solvent action into two fractions, the higher melting fraction wax xpassirig downwardly through the tower together with a minor amount of dissolved extraction solvent and additive, and being withdrawn therefrom below the level of the dotted line I2 representing the higher melting wax phase relatively free of entrained, immiscible solvent and additive. The raffinate phase comprising the higher melting wax and dissolved solvent'and additive ,is passed from the bottom of tower I through valve-controlled pipe I3 into a vacuum evaporator or still I4 wherein the solvent and additive is removed from the higher melting wax by vaporization, the solvent and additive vapors pasing through pipe I 5 into fractionating tower I 6 provided with a reboiler or heating coil I 'I, while the higher melting wax is'drawn from the bottom of evaporator I4 and delivered by valve-controlled pipe I8 into storage Vessel I9. Such wax fraction was white in color, and had a substantially higher melting point and a lower oil content than the wax stock originally charged.

The extract phase comprising the lower melting wax fraction, color bodies, oil, and the major portion of the extraction solvent and additives is withdrawn from the upper section of tower I above the level of the dotted line 2!! representing the extract phase relatively free of entrained, higher melting wax. The extract phase is delivered by valve-controlled pipe 2I into a vacuum evaporator or, still 22 wherein the solvent and additives are vaporized from the lower melting wax, the latter being. drawn fromthe bottom of the evaporator and passed by valve-controlled pipe 23 to storage vessel 2 4 ;The lower melting wax was brown in color andhad a substantially lower melting point and a higher Oil content than the original waxy mixture.

The solvent and additive vapors are passed from the top of evaporator '22 through pipe 25 into fractionating tower I6, wherein such vapors, together with those introduced through pipe I5, are fractionated, the extraction solvent, 1. e., acetone, being taken overhead as vapor through pipe 26, condensed in condenser 2'! and returned by pipe 28 to solvent storage vessel 3. A portion of the condensed solvent may be returned to the top of tower I6 by valve-controlled pipe 29 as reflux. The additive, i. e., aniline, separated from the acetone by fractionation in tower I6, is taken from the bottom of tower I6, as liquid, and is returned by pipes 3| and 30 to the additive storage vessels 6 and 9, respectively.

Depending upon the temperature of operation, the first additive may be introduced somewhat below the point of introduction of the liquefied wax stock, for example, by means of valvecontrolled pipe III'rather than through valvecontrolled pipe Lin which case the secondaddi tive may be admitted through either or both of valve-controlled pipes. "I. and. 8 above the point of introduction'of the wax stock. -In general, the railinate wax phase withdrawn. from the extraction tower will contain froin5% to 25% ofsolv'entand additive, while the extract wax phase will contain from. 55% to of solvent and additive. I

In the event that the extraction is to be carried out in a multi-stage batch countercurrent sys tem, for example, a four-stage system using the solvent and additivesspecifically set forth above, the wax stock would be introduced into the first stage extractor, the extraction solvent (acetone) would be introducedinto the fourth stage extractor, and the first additive, i. e., aniline, would be introduced into the first stage extractor. The second additive, e. gr, aniline, would be introduced into the second stage extractor. The extract phase is withdrawn from the first stage, while the raifinatephase would be removed from the fourth stage extractor. Thetemperature would increase progressively from the first stage to the fourth stage, using the waxy. stock, solvent, and additives described hereinabove; It is to be understood, of course, that the quantities and composition of the solvent and of the additives may be varied within certain limits. a r

Exemplary of the solventand additive materials which may be used in accordance with this invention is the following, the quantities bein volumes per unit volume of wax stock.

acetone 4=I:0.5 vols.-. aniline 0.5i0l vols.

aniline 0.55:0.1 vols.

The present invention is further illustrated by the following example, which, however, is not to be construed as limiting the scope thereof.

(1) A slack wax 'having a' melting. point of 113 F. and an oil content of 24.2% by weight was extracted in a system similar toythat shown in the accompanying drawing, the extraction solvent comprising 4 volumes of acetone, the first additive comprising 0.5-volume of aniline, and the second additive comprising 0.5 volume of aniline. The slack wax was introduced into tower I by pipe 2, the solvent by pipe 4 and manifold 5, the first additiveby pipe I and the second additivejbycpipe 8. The temperature in the extraction tower; was maintained constant Charge Raflinate Extract Weight Per Cent Yield Wax, 100 Wax, 69.0 Wax, 31.0 Per Cent Per Cent Per Cent Melting Point, F 113.1 123.3 76.5 Gil Content, Wt. Per Cent. 24.2 0.1 78.0 Refractive Index at 176 F 1.43625 1.43068 1.46173 A. P. I. Gravity 40.5 41.6 31.2 Color Brown White Dark Brown Firmness i1 Good I Nil Tackiness" Poor Good Nil Plasticity... Too Soft Good Too Soft Fiber Lengt Short Long Short Flexibility Poor Good N i] Where the extraction operation is conducted in a tower, it has been found that a tower having a height of about 40 feet and a diameter of 6 feet is satisfactory. The tower is provided with suitable packing to within about 4 feet of the top and bottom thereof, such spaces functioning as quiescent zones in which entrained materials are permitted to separate from the raflinate and extract phases, respectively. In such a tower, the wax stock is charged at a point about 13 feet from the top thereof, or approximately A; the distance from the top of the tower. The extraction solvent is charged just above the lower level of the packing, for example. 3 to 4 feet from the bottom of the tower. The first additive may be introduced adjacent the point of introduction of the wax stock, for example, 2 feet above or below the wax inlet. The second additive is introduced approximately 2 feet above the point of introduction of the first additive. These values may be altered somewhat, depending upon the tower design, the solvent and additives used, and the temperatures maintained at various levels in the tower. The rafllnate phase is withdrawn from the bottom of the tower, and the extract phase from the top thereof, the extraction solvent being less dense than the wax stock.

I claim: g

1. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises countercurrently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction containing solvent and additives, and the other comprising solvent and additives and the lower melting wax fraction, separating the phases from one another, and removing the solvent and additives from each, the solvent being introduced into the extraction zone near the point of withdrawal of the higher melting wax fraction, the first additive being introduced adjacent the point of introduction of the wax-containing mixture, and the second additive being introduced between the point of introduction of the first-additive and the point of withdrawal of the lower melting wax fraction, the solvent comprising 3.5 to 4.5 volumes of acetone per volume of wax-containing mixture, the first additive comprising 0.4 to 0.6 volumes of aniline per volume of waxcontaining mixture, and the second additive comprising 0.4 to 0.6 volumes of aniline per volume of wax-containing mixture.

2. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises countercurrently contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction with minor amounts of solvent and additives, and the other comprising the lower melting wax fraction with major amounts of solvent and adand removing the solvent and additives from each, the solvent being introduced into the extraction zone near the point of withdrawl of the higher melting wax fraction, the first additive being introduced between the point of introduction of the wax-containing mixture and the point of withdrawal of the lower melting wax fraction, and the second additive being introduced between the point of introduction of the first additive and the point of withdrawal of the lower melting wax fraction, the solvent comprising 3.5 to 4.5 volumes of acetone per volume of wax-containing mixture, the first additive comprising 0.4 to 0.6 volumes of aniline per volume of wax-containing mixture, and the second additive comprising 0.4 to 0.6 volumes of aniline per volume of wax-containing mixture.

3. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises countercurrently I contacting said wax-containing mixture in an extraction zone with an extraction solvent and solvent additives at a temperature such that two immiscible liquid phases are formed, one comprising the higher melting wax fraction containing solvent and additives. and the other comprising solvent and additives and the lower melting wax fraction, separating the phases from one another, and removing the solvents and additives from each, the solvent being introduced into the extraction zone near the point of with drawal of the higher melting wax fraction, the first additive being introduced adjacent the point of introduction of the wax-containing mixture, and the second additive being introduced between the point of introduction of the first additive and the point of withdrawal of the lower melting wax fraction, the solvent comprising 3.5 to 4.5 volumes of acetone per volume of wax-containing mixture, the first additive comprising 0.4 to 0.6 volumes of aniline per volume of waxcontaining mixture, and the second additive comprising 0.4 to 0.6 volumes of aniline per volume of wax-containing mixture.

EDGAR W. CLARKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Number Name Date 2,017,432 Bahlke Oct. 15. 1935 2,160,930 Whiteley et a1 June 6, 1939 FOREIGN PA'IENTS Number Country Date 413,307 Great Britain July 11. 1934 

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTIONS OF HIGHER AND LOWER MELTING POINT, WHICH COMPRISES COUNTERCURRENTLY CONTACTING SAID WAX-CONTAINING MIXTURE IN AN EXTRACTION ZONE WITH AN EXTRACTION SOLVENT AND SOLVENT ADDITIVES AT A TEMPERATURE SUCH THAT TWO IMMISCIBLE LIQUID PHASES ARE FORMED, ONE COMPRISING THE HIGHER MELTING WAX FRACTION CONTAINING SOLVENT AND ADDITIVS, AND THE OTHER COMPRISING SOLVENT AND ADDIRIVES AND THE LOWER MELTING WAX FRACTION, SEPARATING THE PHASES FROM ONE ANOTHER, AND REMOVING THE SOLVENT AND ADDITIVES FROM EACH, THE SOLVENT BEING INTRODUCED INTO THE EXTRACTION ZONE NEAR THE POINT OF WITHDRAWAL OF THE HIGHER MELTING WAX FRACTION, THE FIRST ADDITIVE BEING INTRODUCED ADJACENT THE POINT OF INTRODUCTION OF THE WAX-CONTAINING MIXTURE, AND THE SECOND ADDITIVE BEING INTRODUCED BETWEEN THE POINT OF INTRODUCTION OF THE FIRST ADDITIVE AND THE POINT OF WITHDRAWAL OF THE LOWER MELTING WAX FRACTION, THE SOLVENT COMPRISING 3.5 TO 4.5 VOLUMES OF ACETONE PER VOLUME OF WAX-CONTAINING MIXTURE, THE FIRST ADDITIVE COMPRISING 0.4 TO 0.6 VOLUMES OF ANILINE PER VOLUME OF WAXCONTAINING MIXTURE, AND THE SECOND ADDITIVE COMPRISING 0.4 TO 0.6 VOLUMES OF ANILINE PER VOLUME OF WAX-CONTAINING MIXTURE. 